The present invention relates to a tape reel assembly for data storage tape cartridge. More particularly, it relates to a tape reel assembly comprised of three separately formed components, including a hub ring configured for optimal storage tape engagement.
Data storage tape cartridges have been used for decades in the computer, audio, and video fields. The data storage tape cartridge continues to be an extremely popular form of recording large volumes of information for subsequent retrieval and use.
A data storage tape cartridge generally consists of an outer shell or housing maintaining at least one tape reel assembly and a length of magnetic storage tape. The storage tape is wrapped about a hub portion of the tape reel and is driven through a defined tape path by a driving system. The housing normally includes a separate cover and base, the combination of which forms an opening (or window) at a forward portion thereof for allowing access to the storage tape by a read/write head upon insertion of the data storage tape cartridge into a tape drive. This interaction between storage tape and head may take place within the housing (for example, with a mid-tape load design), or the storage tape may be directed away from the housing to an adjacent area at which the read/write head is located (for example, with a helical drive design or a leader block design). Where the tape cartridge/drive system is designed to direct the storage tape away from the housing, a single tape reel assembly is normally employed. Conversely, where the tape cartridge/drive system is designed to provide head/storage tape interaction within or very near the housing, a two- or dual-tape reel assembly configuration is typically utilized.
Regardless of the number of tape reel assemblies associated with a particular data storage tape cartridge, the tape reel assembly itself is generally comprised of three basic components; namely, an upper flange, a lower flange, and a hub. The hub forms an outer winding surface about which the storage tape is wound. The flanges are disposed at opposite ends of the hub, and are spaced to approximate the height of the storage tape. Notably, the tape reel assembly associated with a single-reel data storage tape cartridge is typically larger in hub and flange diameter, and is more rigidly constructed than the tape reel assembly employed with a dual-reel data storage tape cartridge. In this regard, a typical tape reel assembly for a single-reel data storage tape cartridge integrally molds the lower flange and hub as a single component, as shown, for example, in U.S. Pat. No. 5,400,981 to Rambosek et al. The upper flange is separately provided (i.e. molded) and secured to the hub opposite the lower flange with an adhesive or weld (such as a sonic weld). As part of the molding process for the lower flange/hub, the hub is formed as a ring and a web of material connected to and extending within an inner diameter of the ring. This additional material may include a series of teeth that can be accessed by a tape drive to stop or "brake" tape reel rotation. For example, Rambosek et al. depicts a web of material extending within an inner diameter of the hub ring, at a lower portion thereof. This additional material web renders the hub non-symmetrical. In other words, a lower portion of the hub includes the web of material, whereas the upper portion does not.
While the above-described configuration of a tape reel assembly for a single-reel data storage tape cartridge is essentially universally accepted, certain potential problems have been identified. For example, the lower flange and the hub have differing optimal design characteristics. The outer winding surface on the hub is preferably round, whereas the lower flange is preferably flat. Because these two components are molded as an integral body, it is difficult to achieve a flat flange surface and a truly circular hub. Additionally, the hub and lower flange must be made from the same material. As a result, it may be difficult to provide the hub with appropriate stiffness for specific storage tape conditions and the bottom flange with wear characteristics required for tape drive interface. Finally, during use, the storage tape will impart a circumferential force or stress along the outer winding surface of the hub. Because the hub is non-symmetrical, the stress associated with this tape-induced force is not uniformly distributed along the hub. It is recognized that the stress associated with winding of the storage tape may cause the hub to collapse slightly. With the above-described hub configuration, the hub will not collapse uniformly, but instead will collapse primarily at the upper portion thereof (assuming a cone shape), leading to a varying tape tension across a height of the storage tape. This non-uniform tape tension may cause tape problems, in the form of rippled edges, etc. Notably, the effects of non-uniform hub ring collapse have become more evident with recently available reduced thickness storage tape media. With these highly thin storage tapes, minimization of tape tension has become increasingly important.
Tape reel assemblies associated with dual-reel data storage tape cartridges do not operate under the same conditions as a single reel configuration. As such, the tape reel assemblies associated with a dual-reel data storage tape cartridge have been made available with at least three separate components, including opposing flanges and a hub. An example of such a tape reel design is shown, for example, in U.S. Pat. No. 5,513,815 to Erickson et al. Even with this three-piece design, however, the hub includes a web of material extending across a diameter of the hub ring. This web prevents the hub from evenly distributing stresses placed upon the outer winding surface by the storage tape, possibly leading to the above-described problems.
Data storage tape cartridges are important tools used to maintain vast amounts of information. To remain competitive, data storage tape cartridge manufactures must continually improve cartridge performance while reducing manufacturing costs. To this end, the "standard" tape reel assembly does not provide for requisite uniform stress distribution, thereby leading to potential concerns. Additionally, single reel designs potentially prohibit formation of flat flanges and a round hub. Therefore, a need exists for a tape reel assembly including three separately manufactured components, including a symmetrical hub.